1. Field of the Invention
This invention relates to a composition which, when coated on the surface of an acrylic resin object, forms a protective layer which is superior to other layers coated on plastics, in general, in surface hardness, and in mar, solvent and stress-crazing resistance.
2. Description of the Prior Art
Generally, because plastics are not high in surface hardness, and in mar or scratch resistance, they are apt to be easily injured to lose their gloss. These defects are serious when the plastics are used for making optical products, such as lenses.
In order to improve these inferior properties, there have previously been proposed many methods of coating organic siloxane compounds on the surface of a plastic object and curing the coating to form a protective layer on the plastic object. The prior methods, however, are not effective to provide a completely satisfactory protective layer.
For instance, a protective layer or a coating made by the prior methods is so brittle that when an attempt is made to improve its abrasion resistance, it tends to crack easily. On the other hand, when an attempt is made to improve its craze resistance, it tends to become lower in its abrasion resistance. Further, prior art coating solutions have too short a pot life to be useful for a long time.